Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into bite-sized 1-inch cubes and place them in a large mixing bowl.
Chop the zucchini into half-moons, slice the red bell pepper into thin strips, and break the broccoli into small florets.
Add all the chopped vegetables into the mixing bowl with the chicken pieces.
In a small jar or bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly to ensure every piece is evenly coated.
Spread the mixture in a single layer on the prepared sheet pan, ensuring the ingredients are not overcrowded to allow for proper roasting.
Bake for 18-22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.